Flexing treatment of textile cords

ABSTRACT

A METHOD AND APPARATUS FOR TREATING TEXTILE CORDS FORMED OF THERMOPLASTIC FIBERS SUCH AS NYLON AND POLYESTER AND ESPECIALLY THE CORDS USED IN THE MANUFACTURE OF PNEUMATIC TIRES WHERE THE CORDS ARE NORMALLY COATED WITH AN ADHESIVE AND HOT-STRETCHED. THE TREATMENT INCLUDES DRAWING THE CORDS LONGITUDINALLY WHILE UNDER TENSION OVER AN EDGE OR OTHER MEANS TO PROVIDE A BEND IN OR TO FLEX THE CORDS AND REDUCE THEIR STIFFNESS.

April 20, 19714 o, a. FuNscH ETAL y 3,575,761

FLEXING TREATMENT oF TEXTILE coRns Filed Jan. 16;1967

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April 20,1971 l o, B, FUNSCH ETAL 3,575,761

FLEXING TREATMENT OF TEXTILE CORDS Filed Jan. 16.1967 l 5 sheets-sheet 2INVENTRS GROvER w. RYE BY OWEN B. FuNscH man 4' ATTORNEYS l, m Y v April20, 1971 y 0, B, FUNSCH ETAL 3,575,761

` FLEXING TREATMENT OF TEXTILE CORDS Filed Jan. 16. 1967 5vSheets-Sheet3 INVENTORS GROVER W. RYE

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pril 20, wl o. a. FuNscH ET AL FLEXING TREATMENT OF TEXTILE CORDS 5Sheets-Sheet 5 Filed Jan. 16, 1967 United States Patent O 3,575,761FLEXING TREATMENT OF TEXTILE CORDS Owen B. Funsch, Akron, and Grover W.Rye, Cuyahoga Falls, Ohio, assignors to The Goodyear Tire & RubberCompany, Akron, Ohio Filed Jan. 16, 1967, Ser. No. 609,502 Int. Cl. B29h17/28 U.S. Cl. 156-199 9 Claims ABSTRACT OF THE DISCLOSURE A method andapparatus for treating textile cords formed of thermoplastic fibers suchas nylon and polyester and especially the cords used in the manufactureof pneumatic tires where the cords are normally coated with an adhesiveand hot-stretched. The treatment includes drawing the cordslongitudinally while under tension over an edge or other means toprovide a bend in or to flex the cords and reduce their stiffness.

BACKGROUND OF THE INVENTION The invention relates to the processing ofcontinuous lengths of textile cords, particularly cords formed ofsynthetic fibers such as nylon or polyester. The invention is especiallyapplicable to the processing of fabric formed of such textile cordsarranged in parallel longitudinal relation and held together by spacedlateral warp threads. Such fabric is used extensively in the reinforcingof rubber laminates such as pneumatic tires.

During a typical processing of textile fabric for reinforcing rubberlaminates, the fabric is coated with a suitable adhesive which bonds therubber to the textile cords of the fabric during vulcanization. Thecords are then dried and hot-stretched to impart the desired physicalproperties, especially to minimize the extensibility. After the coatingand hot-stretching, the fabric is passed through calender rolls where anuncured rubber ply compound is applied to both sides to form arubberized sheet.

The resulting product is then cut to size, and laminated to form adesired raw or uncured rubber article such as as uncured pneumatic tire.In forming a conventional pneumatic tire a plurality of plies arewrapped around a tire building drum or form and annular metal beadsplaced adjacent each end of the resulting generally cylindricallaminate. The end portions of the cylindrical laminate spaced outwardlyfrom the beads are then turned either up and back over the beads or downand back under the beads and pressed against the adjacent plies. In thecase of larger tires such as truck tires the stiffness of the pliesoften requires that the operation of turning back the ply ends be done afew plies at a time rather than all at once. After a band of uncuredtread rubber is applied the uncured tire is shaped and vulcanized.

The operation of turning up or turning down the ends of the cylindricalplies around the beads presents unique problems when synthetic fiberssuch as nylon and polyester are used for the reinforcing cords becausewhile the cords are not particularly stiff before being dipped andhot-stretched they are quite stiff afterwards, and are alsosubstantially impervious to air.

Due to the stiffness of cords, the plies may resist the sharp foldaround the beads and in some instances do not bend sharply enough toconform closely to the beads. Consequently, air is occasionallyentrapped between the plies adjacent the beads. This condition isespecially undesirable since the entrapped gases expand and may damagethe tire carcass during or after vulcanization.

The textile cords of tire cord fabric are pervious to gas before beingcoated with an adhesive and hot-stretched ice since the individualfilaments of the cords are generally round in cross-section and defineinterstices with the adjacentfilaments. The adhesive coating, however,tends to seal the outside of the cords making them substantiallyimpervious. Also, the hot-stretching tends to deform the filaments ofthe cords in cross-section so that they are more nearly polygonal andtend to t together in close conformance with adjacent filaments. Theresult of this is a substantial reduction in any ability of the cord toabsorb the gases.

The present invention overcomes the difficulties indicated above andaffords other features and advantages not obtainable from the prior art.

SUMMARY OF THE INVENTION According to one aspect of the invention,textile cords to be used in reinforcing rubber laminates are processedby the method comprising:

( l) tensioning a textile cord, and

(2) drawing the tensioned cord longitudinally across a cord flexingmember defining a relatively sharp bend, the cord being flexedprogressively along its length at the bend while passing across themember.

In the preferred form, the bend has a radius of curvature which is quitesmall but greater than the minimum radius of flexure which the cord canaccommodate without experiencing physical injury. The tension maintainedin the cord is sufficient to place the cord in close conformance withthe bend defined by the flexing member.

Where the invention is used in the processing of fabric formed ofparallel continuous textile cords to be embedded in rubber and used toreinforce laminated rubber articles, the method comprises:

(l) tensioning a continuous web of the fabric,

(2) drawing the tensioned web longitudinally across a cord flexingmember defining a relatively sharp bend, the cords of the web beingflexed progressively along their length at the bend while passing acrossthe member,

(3) embedding the web in uncured rubber to form a rubberized sheet,

(4) forming a laminated article of the sheet, and

1 (5) vulcanizing the article.

In connection with the processing of thermoplastic cord, the flexing ofthe cords while under tension is advantageously accomplished after thecords have been hotstretched and cooled. Where the web is coated with anadhesive during the processing, the flexing is advantageouslyaccomplished after the coating has dried on the cords.

The apparatus of the invention is used in connection with equipment fortensioning and conveying a continuous web of fabric formed of parallelcontinuous textile cords and comprises a cord flexing member extendingtransversely of the web, and means for supporting the cord flexingmember whereby the member engages and flexes the tensioned web beingconveyed.

According to one form of apparatus of the invention, the cord flexingmember is a tubular bar supported by spaced parallel arms connected atone end to opposite ends of the cord flexing member and supported attheir other ends for pivotal movement about a common axis. Means areprovided for pivoting the arms between a position wherein the cordflexing member is out of engagement with the web and a position whereinthe cord flexing member is in engagement with the 1web to displace theweb out of its normal path of travel and thus effect a change indirection in the fweb.

According to another form of the apparatus of the invention, a pluralityof cord flexing members are provided, each extending transversely of theweb. The flexing members are positioned so that the web is constrainedto move through a zig-zag path of travel.

The invention also contemplates a web of fabric comprising parallelcontinuous textile cords formed of thermoplastic fibers, the cordshaving been hot-stretched and thereafter drawn, while under tension,across a cord flexing member according to the method summarized above.The types of thermoplastic fibers include but are not limited to nylonand polyester.

The invention also contemplates a sheet of reinforced rubber comprisinga web of fabric as described above embedded in uncured rubber, and alsoa reinforced rubber laminate comprising superposed plies made up of suchsheets of reinforced rubber, the laminate having been vulcanized. Aparticular reinforced rubber laminate which the invention contemplatesis a pneumatic tire, the tire so constructed having improved flexurecharacteristics and affording a softer ride than a tire made withconventionally processed cords.

The principal advantages of the invention as applied particularly topneumatic tires reside, first of all, in the improved facility withwhich the ends of the cylindrical plies formed during the building of atire on a tire building drum may be turned around the metal beads andfolded against the adjacent plies. The reduced stiffness enables theplies to bend into close conformance with the beads so that entrappedair pockets are minimized With a resulting reduction in defective tireswhich must be rejected.

Secondly, it is believed that the flexing of the cords after beingdipped and hot-stretched tends to rupture the otherwise imperviouscoating of adhesive and also tends to work the filaments of the cordsout of close conformance to one another and thus enlarge the intersticesbetween them. Consequently, it is believed that the pressure of any gaswhich may be entrapped in the plies may be relieved while the tire is inthe vulcanizing mold or press, through the release of gas into thereservoir provided by the cords.

Thirdly, the flexing of the cords reduces their stiffness while at thesame time unexpectedly improving their physical characteristics such asbreaking strength and fatigue resistance. Also, the resulting tire ismore flexible and provides a more comfortable ride.

It is among the objects of the invention to improve the processabilityof sheet material or plies formed of textile cords embedded in uncuredrubber.

Another object of the invention is to reduce defects which occur duringthe vulcanizing of pneumatic tires and rubber laminates due to theexpansion of gas entrapped between the plies.

A further object of the invention is to provide improved folding of cordreinforced plies over the metal beads used in the construction ofpneumatic tires.

Other objects, uses and advantages of the invention will be apparentfrom the following detailed description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. l is a plan view with partsbroken away and shown in section of an apparatus for practicing themethod of the invention;

FIG. 2 is a sectional view taken on the line 2-2 of FIG. l;

FIG. 3 is an end elevational View on an enlarged scale with parts brokenaway and shown in section, of a fabric flexing bar of the apparatus ofFIG. l;

FIG. 4 is a sectional view with parts broken away taken on the line 4-4of FIG. 3;

FIG. 5 is an elevational view showing another fabric flexing apparatusfor practicing the method of the invention;

FIG. 6 is a schematic diagram of a fabric processing line, includingequipment for processing fabric according to the invention;

FIG. 7 is a greatly enlarged somewhat diagrammatic cross section of aportion of a textile cord which has not 4 yet been processed for use inreinforcing rubberized laminates;

FIG. v8 is a similar cross section of a portion of a textile cord suchas shown in FIG. 7 which has been coated with an adhesive andhot-stretched according to conventional tire cord processing methods;

FIG. 9 is a similar cross section of a portion of a textile cord whichhas been subsequently treated according to the invention;

FIG. 10 is a view illustrating in diagrammatic form the angularrelationships involved in the flexing of a textile cord according to theinvention; and

FIG. ll is a view similar to FIG. 10 and on the same scale,illustratingV the angular relationships involved in the flexing of atextile cord according to the invention but with a smaller radius ofcurvature.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the drawings FIGS. l to 4show a fabric flexing apparatus A for practicing the method of theinvention. The apparatus is shown as being incorporated in a tire cordfabric processing line wherein a continuous web of tire cord fabricformed of parallel longitudinal textile cords is coated with anadhesive, dried and hot-stretched prior to being passed through calenderrolls where the web is embedded between layers of uncured rubber (FIG.6). The apparatus is preferably located at a position in the line wherethe fabric has already been coated with an adhesive, dried andhot-stretched, and where the tension in the cords is relatively low, forexample from .5 to 4 lbs. per cord for conventionol nylon cords forpassenger car tires. The location shown in FIG. 6, just prior to thecalendering unit is particularly suitable.

The apparatus A comprises two parallel frame members 10 that supportidler rolls 11 and 12 at opposite ends of the apparatus which areadapted to guide a continuous web 13 of tire cord fabric. The rolls 11and 12 are mounted in bearings 14 secured to the bottom of the framemembers 10 as shown in FIG. 2. Extending between the frame members 10parallel to one another and perpendicular to the path of travel of thetire cord fabric 13 are three stationary tubular supports 15 spaced fromone another, and two adjustable tubular supports 16 located in thespaces between the supports 15.

Each of the supports 15 and 16 has secured thereto a fabric flexing bar17 which extends longitudinally along each support 15 and 16 from end toend and which is L-shaped in cross section. The apex of each bar 17faces away from its support and defines an edge 18 formed with a radiusof about .050 inch, the edges being adapted to engage the fabric web 13and flex it according to the invention. The bars 17 face downwardly fromthe tubular supports 15 and upwardly from the tubular supports 16 asshown in FIG. 2. Accordingly, the path of travel of the fabric web 13through the apparatus A follows a zigzag course with the fabric bendingaround the edges 18.

The adjustable tubular supports 16 are carried at each end by slideblocks 20 received in vertical guides 21 secured to the frame members10. FIGS. 3 and 4, illustrate the attachment of the adjustable tubularsupports 16 to the slide blocks 20, the supports 16 being welded orotherwise secured at each end to carrier plates 22 each of which ismounted on a bearing 23 which is journaled at its opposite end in abushing 24 mounted in the slide block 20. Each carrier plate 22 has apassage 25 formed therein which communicates with the interior of atubular support 16 and which provides an access for a cooling fluid forcooling the supports 15 and 16.

The supports 16 are mounted for rotary movement relative to the slideblocks 20 as indicated and are biased to the position shown in FIGS. 3and 4 by means of coil tension springs 26. Each spring 26 is supportedat one end on a pin 27 secured to a bracket 28 mounted on the carrierplate 22. The other end of the spring 26 is supported on a pin 29mounted on a rod 30 secured to the slide block 20. The springs serve todampen the initial stress exerted on the fabric during changes in linespeed and when the vertical positions of the supports 16 are changedwhile the fabric web 13 is in motion.

Vertical adjustment of the slide blocks 20 is accomplished by means ofscrew jacks 32, the jacks each comprising a threaded plunger 33, a topplate 34 which engages a slide block 20, and a helical gear 35. Thehelical gear is threaded on the plunger 33 and mounted for rotarymovement so that turning of the helical gear 3S either raises or lowersthe plunger 33. The teeth of the helical gear 35 are engaged by a worm36 mounted at the end of a drive shaft 37. The drive shafts 37 extendfrom opposite ends of bevel gear units 38 driven by motors 39.Accordingly, the motor 39 may be used to adjust either of the supports16 to a desired height for obtaining the desired angle of flexure forthe fabric web 13 as it passes through the apparatus A.

FIG. shows another type of fabric fiexing apparatus B adapted for use inpracticing the method of the invention. The apparatus B is adapated forinstallation in existing fabric conveying equipment with a minimum ofstructural modification. The existing equipment includes means forconveying a continuous web 40 of tire cord fabric which includes a frameformed of structural members including horizontal members 41 andvertical members 42, the members 41 and 42 on only one side of the framebeing shown in FIG. 5. The vertical member 42 supports bearing mounts 43which carry rolls 44, the web 40 being wrapped around the rolls 44 asshown and passed to other portions of the fabric conveying equipment.Mounted below each horizontal frame member 41 is a structural beam 45each of which supports one end of three idler rolls 46, 47 and 48mounted in bearing mounts 49, 50 and 51. The bearing mounts 49, 50 and51 support the idler rolls 46, 47 and 48 which guide the fabric web 40in the manner shown. Extending outwardly from each of the bearing mounts50 are pins 52, each of which carries a bell crank 53. A tubular support57 extending laterally across the apparatus B parallel to the idlerrolls 46, 46 and 48 is mounted between the ends of one arm 54 of eachbell crank 53. Secured to the support 57 and extending longitudinallybetween the ends thereof is a fabric flexing bar 58 mounted with itsapex extending upwardly from the support 57. The apex of the bar 58provides a fiexing edge 59 that is formed with a radius of curvature ofabout .050 inch. The bell cranks 53 at each end of the frame 41 aremovable between a fabric fiexing position shown in solid lines in FIG. 5and an inoperative position shown in dashed lines in FIG. 5. Themovement between the two positions is accomplished by means of hydrauliccylinders 60, one being mounted on each side of the frame. Each cylinder60 has a piston rod 61 pivotally connected to an arm 62 of the bellcrank 53. A bolt 63 received in a threaded opening in a bracket 64serves as an adjustable stop which limits the fabric flexing position ofthe bar 58. When the fabric flexing bar 58 is in the flexing position itengages and flexes the fabric web 40 between the rolls 47 and 48 so thatthe fabric defines an included angle of about 100.

OPERATION FIG. 6 shows diagramatically a typical tire manufacturingprocess according to the invention wherein a fabric web comprisingparallel longitudinal cords formed of textile fibers such as nylon orpolyester is first treated according to conventional practices wellknown in the art prior to being embedded in uncured rubber. FIG. 7illustrates the condition of the fibers or filaments of a typical nyloncord before being processed. It will be seen that the fibers aregenerally round in cross section and define interstices extendinggenerally longitudinally of the cord. The treatment shown includesdipping the fabric web in an aqueous dip to coat the cords with anadhesive that serves to bond the cords to the rubber during thevulcanizing process. Immediately thereafter the web is conveyed by rollsthrough a drying step and then passes through a heat treating oven. Asthe web leaves the oven it is normally cooled by the ambient air to roomtemperature. At this stage the cords, particularly those formed of nylonand polyester fibers, are very stiff. FIG. 8 illustrates the conditionof a nylon cord processed according to conventional practices and itwill be seen that the cross section of the fibers is generally hexagonalin form and that the volume of the interstices shown in FIG. 7 isgreatly diminished. Also the adjacent surfaces of the fibers conformclosely to one another.

According to the method of the invention, a fabric flexing apparatussuch as one of the two types described above is located in the path oftravel of the fabric web and the web is drawn across one or more flexingedges of the apparatus while under tension. The tension in the cords mayvary depending on the size of the cord and the type of fiber. Where arelatively low tension is used such as less than l 1b. per cord,improved results can be obtained by passing the cords across more thanone flexing edge.

The flexing serves to greatly reduce the stiffness of the cords andappears to render the cords more pervious to gas FIG. 9 illustrates thecondition of the cord of FIGS. 7 and 8 after being processed accordingto the method of the invention. It will be seen that the fibers are notas tightly compacted as those of FIG. 8 and it appears that the volumeof the interstices between the fibers has increased. It appears probablethat any tendency of the fibers to adhere to each other is diminished bythe treatment. The reduction in stiffness is readily apparent from avisual comparison of the tendency of a cord to bend under its ownweight. An untreated cord will resist bending under its own weight to aconsiderable extent while in comparison a treated cord is quite limp andhas very little resistance to bend.

After the fabric has been so treated it is conveyed to a calenderingunit where a layer of rubber is applied to form a reinforced rubbersheet (FIG. 6). The resulting rubber sheet material is normally cutdiagonally and spliced as is common in the tire building art, orotherwise processed, after which it may be cut to size and used in theconstruction of an uncured rubber laminate such as a pneumatic tire. Thelaminate is then vulcanized according to standard practices in the art.

The improved flexibility of the ply material facilitates the forming ofthe rubber laminate and reduces the tendency of any gas trapped betweenthe ply to damage the walls of the tire carcass, the pervious cordstending to provide a reservior-for the expanding gas.

The method of the invention is also beneficial in the processing oftextile cords used in reinforcing rubber` laminates where the cords arenot coated with an adhesive, such as where a bond producing chemical isadded to the rubber composition which is calendered onto the cords.

While the invention is especially adapted to reduce the stiffness of thecords it has been found that flexing also improves fatigue resistance,

The practice of the invention and the advantages deriving therefrom maybe better understood from the following examples:

EXAMPLE l Two fabric webs each 52 Wide and comprising about 1980parallel continuous tire cords of N-44 nylon, 1300/ 2 (in other wordseach cord was made up of two yarns of 1300 denier each) were processedunder two different sets of conditions, one set being according toconventional prior art practices and the other set being according tothe method of the invention.

The conventional process comprised dipping the fabric web in an aqueousdip where it was coated with an adhesive, drying the web and thereafterhot-stretching the web in a conventional hot-stretching oven. The webwas then passed through calender rolls where a layer of uncured rubberwas applied to both sides to form an elongated rubber sheet. The sheetwas cut on a diagonal into separate sections and spliced along splicelines parallel to the cords. The resulting product was used to form theplies of a pneumatic tire according to methods well known in the art.

The other fabric web was processed according to the conventionalpractice indicated above except that after heat treating it was treatedaccording to the method of the invention. The treatment comprisedpassing the web at a rate of yds. per min. across one 0f thelongitudinal edges of each of three stationary two-inch square steelflexing bars. Each edge over which the web passed flexed the web todefine an included angle of about 120, the web following a zig-zag pathof travel between the three bars. A web tension of about 900 lbs. (orabout .5 lb, per cord) was maintained throughout the passing of thefabric across the bars. The cords had a diameter of about .030 inch.

Prior to calendering the fabric of both the conventionally processed weband the web passed through the flexing bars, was tested to determine andcompare certain physical characteristics. The specific tests and dataobtained therefrom are shown below in Table I.

In Table I, the break strength, modulus, and elongation at break weremeasured using an Instron Tensile Tester, the measurements being takenwith specimen cords which had been kept in a desiccant atmosphere for 24hours before testing. The two modulus measurements represent the loadfirst at an elongation of 5% and then at an elongation of The breakstrength and elongation at break of each cord tested were measuredaccording to standard practice.

The stiffness of the specimen cords was measured using a GurleyStiffness Tester (Motor Operated Model No. 4171) sold by W. and L, E.Gurley Inc. of Troy, N.Y. One inch wide specimens of fabrics were usedto obtain a stiffness measurement in milligrams per inch. The figureobtained was then divided by the number of cords per inch to obtain thestifl'ness in milligrams per cord.

The durability was measured according to a method described as GoodyearTube Fatigue Method on pages 185 through 188 of 1966 Book of ASTMStandards- Part .Z4-Textile Materials-Yarns, Fabrics and General Methodspublished by American Society For Testing and Materials, 1916 Race St.,Philadelphia, Pa.

The data in Table I indicates the unexpected improvement in physicalproperties of the cords deriving from the method of the invention. Theimprovement in fatigue resistance or durability was the most surprising.No undesirable effects were noted. Tires constructed with the fabric webtreated according to the method of the invention were easier tofabricate (especially as to the folding of the plies around the beads)and defects resulting from entrapped air were reduced markedly and inmany cases eliminated.

EXAMPLE II Several 1260/3, Nylon 66 tire cords which had been coatedwith an adhesive and hot-stretched according t0 conventional practice,were tested before and after being flexed under varying conditions oftension, using laboratory apparatus adapted for practicing the method ofthe invention, Each cord had a diameter of about .027 inch and wassecured at one end to a weight of from 1.0 to 5.0 lbs. With the weightserving to tension the cord, the cords were drawn one time over a rodhaving a diameter of .106 inch, which flexed the moving cord so as todefine an included angle of about The stiffness of each cord after thepass over the rod was determined and recorded, the measurements beingmade on a Gurley Stiffness Tester. The results were cornpared withcorresponding measurements made with unflexed cords.

The test results are presented in Table II below.

Another set of tests was made using the same procedure with the nyloncords subjected to a tension of 1 lb. in each case but with rods ofdifferent diameters. The test results are presented in Table III below.

TABLE III Stillness (milligrams) Rod Reduction diameter Unflexed Flexedln stiffness (Inches) cord cord (percent) From Tables II and III it willbe seen that the stiffness of a previously conventionally hot-stretched,or heat treated, and adhesive coated nylon cord is very materiallydecreased by processing of the cord in accordance with this invention.At the same time the desired physical characteristics of the cord arenot adversely affected and at least some may be enhanced. The method ofachieving this marked increase in flexibility of tire cord or fabric andthe results obtained are dependent on several factors. These factorsinclude the cord material, diameter, and construction; thecord-to-rubber bonding agent or adhesive, if used; the previous heattreatment of the cords; the tension the cord during the processing inaccordance with this invention; the included angle of the cord definedby the portions of the cord immediately adjacent the opposite ends ofthe flexing edge; the radius of curvature of the flexing edge, or moreparticularly sharpness of the bending of the cord; and the frequency ofbends per inch of cord provided along the cord.

Where it is desired to incorporate this invention in an existing cordprocessing unit by modification of existing apparatus and withoutchanging the overall operation of the system, it might be consideredthat the cord physical characteristics including the cord material,dimensions, etc., are constant, as are the previous heat treatment ofthe cord, the adhesive used, or the lack of such adhesive, the cordtension and the temperature and lineal speed of the cord. In that eventthe degree of fiexibility increase which will be obtained will bedirectly related to the degree of bending of the cord and to thesharpness of the bending of the cord which is determined by the degreeof bending and the radius of curvature at the bend. For example, andwith reference to FIG. 10, if a cord C is partially wrapped about a fiexinducing member F, which for purposes of illustration is a circularcross-sectioned bar having a radius R1, the radii of the bar at thepoints of tangency of the cord to the bar will define what may bereferred to as the wrap angle X1 of the cord. Also the portion of thecord extending from the bar from the points of tangency thereto willdefine an included angle Y1. The angle Y1 is the supplement of the wrapangle, or in other words when the wrap angle is 80 the included anglewill be 100. Also, the included angle Y1 is the supplement of the angleZ1, which is the angle that the cord is bent and represents the changein direction of the cord over the bend. It will be seen that the wrapangle X1 and the bend angle Z1 are equal.

For a given bar radius R1 and a given included angle Y1 the cord willengage the bar over an arcuate dimension or length of contact indicatedat L. The length of contact as indicated at L and the included angle Y1will determine the extent of bending as well as the sharpness or rate ofbend of the cord. For example, and with reference to FIG. 10, if thecord C with a bend angle Z1 and a length of contact as indicated at Lundergoes a given increase in flexibility, a greater increase infiexibility will be obtained if the wrap angle is increased to thatshown in broken lines in FIG. 10, even through the radius of curvatureover the bend (or R1) is maintained constant. This is because the bendangle Z2 is larger. However, in this instance the sharpness of bendingof the cord will not be increased. On the other hand, and with referenceto FIG. 11, if the same cord C is engaged over a bar F1 having a radiusR2 which is smaller than the radius R1 of the bar F of FIG. 10 andassuming the bend angle Z1 and the wrap angle Y1 are maintained, thesame as indicated in FIG. 10, the length of contact over the bend, asindicated at L-2, will be smaller than the length of contact indicatedat L; thus the rate of change of direction of the cord over the portionthereof undergoing the bend, or in other words the sharpness of thebend, is increased, resulting in an increase in the flexibilityobtained.

The foregoing is further illustrated by reference to Table III whereinit Will be observed that the reduction in stiffness decreased as the roddiameter was increased and the cord tension and bend angle maintainedconstant. Accordingly, one may vary the fiexibility increase obtained bythis invention by varying either or both of the bend angle Z and thelength of the cord over which the change' in direction or bending isaccomplished Generally speaking, the sharpness of bending should besufficiently high to accomplish the desired flexibility increase but notso high as to result in damage to the cord.

As noted above, the particular bend angle and radius of bend, may varywith, or depending on, other factors mentioned above as affecting thedegree of increase in flexibility obtained. For example, the foregoingTables I, II, and III dealt with increasing the iiexibility of nyloncord. The invention is equally applicable to cords of polyester or otherthermoplastic materials suitable for use in tire cords. Also theinvention may be advantageously used in connection with other tire cordmaterials where an increase in flexibility of the cord fabric isnecessary, or desirable. In this connection, while the reason for themarked increase in flexibility of nylon and polyester cords obtained bythe use of this invention is not completely understood, it is believedthat it is due primarily to two factors. Firstly, Where a cord-to-rubberbonding agent is applied to a cord made of a multiplicity of very finefilaments, the bonding agent tends to provide a film over the cord andalso tends to penetrate into the cord. The degree of penetration of theadhesive into the cord may vary from a small amount to completepenetration so that each of the filaments is coated. The lattersituation may be the case where the cord material is glass, and it isdesired to coat each filament to prevent abrading engagement betweenadjacent filaments. In any event, the adhesive, when dried, not onlytends to prevent gases from penetrating the cord but also becomesbrittle and may contribute to a very substantial degree to the stiffnessof the cord. When adhesive coated cord is treated in accordance withthis invention there is a tendency to provide micro fractures in thefilm over the cord and also a tendency for any adhesive bonds betweenfilaments to be broken so as materially to reduce the stiffness of thecord occasioned by the adhesive. Also the sharp bending of the cord isbelieved to effect a change in the physical characteristics of theadhesive rendering it more flexible. In the processing of tire cord ortire cord fabric, it is normally the practice to hot-stretch, or heattreat, the cord or fabric. This treatment is usually performed after thelaments have been formed into a cord. In many cord processing operationsthe cords are coated and heat treated twice, in which case the fiexingof the cord may be accomplished after each separate heat treatment oronly after the last. The purpose of hot-stretching or heathtreating tirecord varies with the type of material being used. However,hot-stretching is primarily used to accomplish (1) a modification of theinternal structure of the fiber to obtain a desired change in physicalproperties, or (2) an elongation of the cord to reduce its potentialelongation in use, or (3) equalizing of the tension on the individualfilaments or fibers to obtain an improvement in the tensile strength ofthe cord. Therefore, where the term hot-stretching or heat treatment isused herein, it is intended to refer to a treatment wherein the materialis heated and placed under tension for the purpose of 0btaining one ormore of the results set forth above.

When cords of thermoplastic material such as nylon, or polyester, arehot-stretched, the filaments undergo a change in cross-sectionalgeometry. With reference to FIG. 7, it has been mentioned that there istherein shown the cross-section of a portion of a nylon tire cord priorto the hot-stretching thereof. It will be seen that the filaments aregenerally circular in cross-section with each filament normallycontacting one or more adjacent filaments. It will be appreciated,however, that in this condition of the cord the filaments are relativelyfree to move each relative to the others and the cord is relativelyflexible. With reference to FIG. 8 there is shown a cross-section of thesame cord as represented in FIG. 7, but after the cord has beenhot-stretched in a conventional manner. It will be readily apparent thatthe hot stretching operation has resulted in a very substantialdeformation of the filaments so that they are now polygonal incross-section being for the most part hexagonal. By and large each fiatface of each filament is engaged with a fiat face of an adjacentfilament and the filaments are now generally in close engagementsomewhat in the nature of a jigsaw puzzle. The cord represented in FIG.8 is very much stiffer as compared to the cord represented in FIG. 7. Itis believed that the very substantial increase in stiffness is broughtabout in part by the generally interlocking relationship of thefilaments which results from the hot-stretching operation. Also, it isbelieved that there is a bond at the interfaces between the filamentswhich bond may be mechanical, chemical, or both. Further, and as notedabove, to the extent that adhesive is present on the filaments beingconsidered, the adhesive itself tends to bond the filaments together andin itself contributes to an increased stiffness of the cord. Withreference to FIG. 9 there is illustrated a cross-section of the cord ofFIG. 8 after being processed in accordance with this invention. It wouldappear from a consideration of FIG. 9 that the sharp bending of the cordwhen it is processed according to this invention has resulted in thebreaking of a very substantial number of any bonds between the flatinterfaces between the filaments and caused increased spacing betweenthe filaments. It is further believed that the sharp bending that thecord undergoes in processing according to this invention cracks orfractures any adhesive films on the filaments thus reducing stiffness ofthe cord contributed by such film. The foregoing explanation of thereasons for the improvement of flexibility obtained with this inventionwould seem to be borne out when it is considered that the training of apreviously hot-stretched tensioned cord around the usual sizes of rollsof conventional cord processing apparatus does not apparently affect thestiffness of the cord or fabric due to the lack of a sharp flexing orbending of the cord.

It should also be mentioned that the treatment of cord or fabricaccording to this invention results in the tendency of the cordcross-section to depart from a generally circular shape and become moreelliptical with the major axis of the ellipse being parallel to thegeneral plane of the fabric. This, of course, will tend to reduce thebending modulus of the cord to provide increased ease of bending thefabric out of its general plane.

From the foregoing it should be apparent that where the termthermoplastic is used in connection with tire and materials to betreated by this invention, the term is being used primarily in the sensethat a filament of such material, when heated and tensioned in anymanner used to process tire cords, will be deformed generally in themanner described in connection with FIGS. 7 and 8.

As has been noted above there are other factors that affect the degreeof flexibility achieved with the process of this invention. The materialfrom which the cord filaments are made will inherently provide a degreeof stiffness dependent upon the particular material. The cord diameter,as it increases, will result in greater absolute values of stiffness,and the degree of bending or sharpness of bending may vary with corddiameter. Further the cord construction will, to some extent, affect themanner of treatment. For example, a cord consisting of two bundles offilaments or yarn may react differently than a cord consisting of threeyarns. The cord-to-rubber bonding agent used will of its own naturecontribute to a varying degree to increased stiffness of the cord andthus determine to some extent the amount by which the stiffness may bereduced by the treatment of this invention. Of course, if such anadhesive is not used, the initial cord stiffness prior to treatment bythe method of this invention will be less than if an adhesive were used.Previous heat treatment to which the cord has been exposed will alsodetermine the absolute stiffness of the fabric before treatment inaccordance with this invention. For example, and generally speaking, anylon cord which is stretched approximately 10 percent in ahotstretching operation will have a substantially greater stiffness thanone stretched 6 percent. As far as frequency of bending of the cord isconcerned, the specific embodiments described above contemplate abending of the cord continuously along its length. However, this is notto say that it is not contemplated that the cord may be flexed atspecified locations or incrementally along the cord rather thancontinuously, and in either event, the cord is flexed progressivelyalong it length. These factors should be considered when determining anoptimum arrangement of a cord flexing apparatus to practice thisinvention and in determining the bend angle, wrap angle and radiuscurvature, radius of bend of the cord, etc.

However, using the foregoing specific examples, it is believed clearlyapparent that one skilled in the art can for any specific cord arrive ata very satisfactory improvement in flexibility with a very minimum ofeffort. For example, and in comparison to the data set forth in TablesII and III above which dealt with nylon cord, similar tests wereconducted on polyester tire cord of 1300/ 3 construction; that is tosay, 3 yarns of 1300 denier each. In these tests, which were conductedin the same manner as the tests the results of which are shown in TablesII and III hereof, the previously heat treated and adhesive coated cordhad a stiffness approximately of 175. After treatment in accordance withthe invention using a rod diameter of .106 inch and a tension of 1 lb.the cord had a stiffness of approximately 33. There was thus achievedapproximately an percent reduction in stiffness when the polyester cordwas treated in accordance with this invention.

As discussed above the invention is particularly adapted for use inprocessing tire cord. However, as also indicated it may have broaderapplication to other cords such as used in reinforcing others types ofrubber laminates. Also, where the term ruber is used, we mean to includenatural or synthetic rubber or blends thereof as well as other materialshaving similar characteristics and uses.

It will be understood that the invention has been shown and describedwith reference to preferred embodiments thereof which are intended forthe purpose of illustration rather than limitation and other variationsand modifications will be apparent to those skilled in the art withinthe intended spirit and scope of the invention, wherefor the patent isnot to be limited to the form herein speciflcally illustrated anddescribed nor in any other manner inconsistent with the progress bywhich the art has been promoted by this invention.

We claim:

1. A method of manufacturing a rubber article incorporating a pluralityof parallel, continuous, filamentary, reinforcing cords comprising:prior to incorporating said cords in said article, applying a liquidcord-to-rubber bonding agent to said cords; drying said agent;subsequent to the drying of said agent, reducing the stiffness of thecords at least about 15 percent by sufficiently sharply flexing thecords progressively along their length while maintaining the cords undera tension of between .5 and 4 pounds per cord; and thereafter embeddingsaid cords in rubber.

2. In a method claim 1, said flexing of the cords being accomplished byeffecting relative movement, in a direction longitudinally of the cords,between the cords and a cord flexing member extending laterally of thecords while said cords are engaged with said cord flexing member andwith the portions of the cords on opposite sides of said cord flexingmember defining an included angle substantially less than degrees.

3. In the method as described in claim 2, said cord flexing memberhaving a cord engageable surface having a radius of curvature of about.050 inch.

4. A method of manufacturing a rubber article incorporating a pluralityof parallel, thermoplastic, continuous, filamentary, reinforcing cordscomprising: prior to incorporating said cords in said article,hot-stretching said cords; subsequent to said hot-stretching, reducingthe stiffness of said cords at least about 15 percent by sufficientlysharply flexing the cords progressively along their length whilemaintaining the cords under a tension of between .5 and 4 pounds percord; and the thereafter embedding said cords in rubber.

S. In the method as described in claim 4, the flexing of the cords beingaccomplished by effecting relative movement, in a directionlongitudinally of the cords, between the cords and a cord flexing memberextending laterally of the cords while said cords are engaged with saidcord flexing member and with the portions of the cords on opposite sidesof said cord flexing member defining an included angle substantiallyless than 180 degrees.

6. In the method as described in claim 5, said cord flexing memberhaving a cord engageable surface having a radius of curvature of about.050 inch.

7. In the method as described in claim 4, the further steps of, prior tohot stretching said cords, applying a liquid cord-to-rubber bondingagent to said cords, and drying said agent on said cords.

8. In the method described in claim 7, said flexing of the cords beingaccomplished by moving said cords continuously in a directionlongitudinally of the cords and across a cord flexing member extendinglaterally of the cords while said cords are engaged with said cord exingmember and while the portions of said cords on opposite sides of saidcord flexing member define an included angle substantially less than 180degrees.

9. In the method as described in claim 8, the cord engaging surface ofsaid cord flexing member having a radius of curvature of approximately.050 inch.

References Cited UNITED STATES PATENTS 1,520,342 12/1924 Grabau 161-1762,509,741 5/1950 Miles 156-229(UX) 3,042,568 7/ 1962 Ludowici et al156-229X FOREIGN PATENTS Canada 156-229 `Great Britain. Great Britain.Great Britain. Great Britain.

BENJAMIN A. BORCHELT, Primary Examiner S. C. BENTLEY, Assistant ExaminerU.S. Cl. XR.

